I just inadvertently found a trick to scroll faster using a scrolling wheel mouse in anything that can be scrolled in KDE application, e.g. in the list of emails in Kmail, in the list of articles in aKregator, in a long web page displayed in Konqueror, in a long text displayed in Kwrite, etc. Just hold the Shift key while scrolling with the mouse’s scrolling wheel: scrolling becomes much faster!